Hi, I thought I would chime in with my recent experience.
I just purchased an Ender 3v2, and it took me 3 days but I finally got klipper installed.
#1 check the chip on your board to verify the GD32F chip.
in menuconfig choose the SWD option.
#2 On my particular board I had to select “USB on PA11/PA12” which is different than the instructions for the “real” STM32. It must be another slight variation of the board.
On my board there was a blue light near the USB interface that lit up when the correct USB setting was used.
#3 I had to use the " /dev/serial/by-path/*" option to get the USB recognized
#4 I ran across 3 different suggestions for the proper filename for flashing. What worked for me was the following convention “firmware-1.bin” the filename is not changed after successfully flashing like on older boards. to reflash you must choose a different filename “firmware-2.bin”. etc. I was able to verify this by reflashing marlin back to the board. after re-flashing klipper I now have the MCU recognized in the mainsail interface.
Extra tip- make sure you have agood USB cable. I had a bad one and didnt know it. Lots of time wasted there.
Hope this helps someone…
-Dave